1. Field of the Invention
The present disclosure is generally related to centrifugal compressors and methods of their manufacture.
2. Brief Description of the Prior Art
Natural gas fields that have been extensively used are characterized by increasingly higher water content, requiring increased use of wet gas treatment and technology. Existing devices are able to pump a two-phase mixture having a volumetric liquid content higher than 5%, but for lower liquid content, a typically bulky and costly separator is required. Axial compressors use fogging and inter-stage water injection in order to reduce compressor work: however, particles are usually atomized to sizes less than 10 mm (millimeter) and the volumetric liquid content is less than 0.1%, making evaporation very fast. Conventional centrifugal or axial compressors are also used to compress a mixture having a significant liquid content under non-conventional conditions such as, for example, water (or even ice) ingestion during takeoff or landing of turbofans and turbojets. However, continuous and prolonged operation under conditions where the liquid content is significant, albeit distributed in big droplets, is challenging due to erosion caused by the impact of the droplets on the impeller blades, corrosion, rotor unbalance and/or loss of efficiency due to the increased friction between the water and the impeller and compressor diffuser.
Traditionally, a first primary separation stage is generally used upstream of the compressor in order to perform a first separation of the gas and the liquid, followed by a second separation stage for separation of the finer droplets. The separation stage can be static and external to the compressor, or dynamic and embedded in the compressor outer case. This allows the compressor to operate on an almost fully gaseous medium and can be designed with standard techniques. The separated liquid is usually removed with a pump. However, these arrangements are typically bulky, complicated and expensive.
Ongoing challenges in the industry include reducing the absorbed power compared to a system having standard dry gas only compressors and separators, reducing the size, weight and cost of the upstream separators, eliminating the need for inter-stage separators, and devising systems using numerous wet-gas centrifugal compressor stages to replace systems having a rotating separator embedded in the compressor or a bulky static separator upstream of the compressor.
This disclosure pertains to the need to more efficiently separate wet gas mixtures in a centrifugal compressor, particularly for volumetric liquid content up to 5%.